— Dependent children may remain on a parent’s insurance plan until they turn 26.

— Many preventive services are now free for all adults, including screening for blood pressure, colorectal cancer, and diabetes.

— Many preventive services are now free for women, including contraception for most insured women, breast and cervical cancer screening and various services for pregnant women.

— Many preventive services are now free for children and adolescents, including many immunizations and screening for blood lead levels, vision problems and STDs.

Because all these and other ACA benefits cost insurance companies huge sums of money, why did the companies generally support the ACA during the intense debate preceding its congressional passage?

The answer is the individual mandate.

By requiring everyone to have health insurance, the ACA promised insurance companies millions of new clients, among them many younger people, who are generally healthy and thus profitable for the companies. Without the individual mandate, the companies would have had little reason to support the ACA, and their opposition would likely have doomed it.

Many people dislike the individual mandate, but the idea of the mandate actually came from the Heritage Foundation, a conservative think tank, in 1989. The concept behind the mandate reflects the conservative emphasis on individual responsibility: because uninsured people can visit an emergency room for medical care, they are in effect “free-loaders” who are saddling hospitals with unpaid services by not taking personal responsibility for paying for their own health care. It was no accident that Massachusetts Republican Gov. Mitt Romney put the individual mandate at the heart of the “Romneycare” health care plan that his state approved in 2006. This plan provided the model for ACA.

The concept behind the individual mandate echoes the reason that almost all states require motor vehicle insurance. If you were in a crash with an uninsured driver, you and your own insurance company would have to pay all repair and health care expenses yourself, with the uninsured driver paying nothing. In effect, you would be paying for this driver’s failure to be responsible enough to be insured.

Yes, the individual mandate involves the government telling us what to do. But so does the requirement that motor vehicle drivers be insured; so does the requirement to pay our fair share of taxes, however much we grumble about doing this; and so does the requirement to have our cars pass state inspection. We certainly don’t want the government to overreach, but all these and many other government mandates are for the greater good.

Yes, the ACA and the individual mandate might represent creeping socialism. But if the ACA is socialism because it represents government intervention into the private sector, then so are the U.S. Postal Service, Social Security and Medicare (as was charged when they were first proposed), public schools and many other government services.

Yes, premiums and deductibles in the ACA’s marketplace plans are often far too high, but the fact remains that more than 20 million people have gained insurance coverage under the ACA and that costly insurance coverage is still better than no coverage at all. And the fact remains, thanks ultimately to the individual mandate, that all insured Americans now have many free preventive services than we ever did before, that we cannot now be denied insurance because of a pre-existing condition and that we cannot now lose insurance because our medical costs have become too high.

These facts yield an inescapable conclusion: Repealing the ACA will harm the health of millions of Americans. Repeal proponents either don’t grasp or don’t care about this hard truth, and they have yet to devise a plan that would avoid its harsh reality. Instead of repealing the ACA, we should try to improve it so all Americans will finally have the affordable health insurance they need and deserve.

Steven E. Barkan is professor and interim chair of the Department of Sociology at the University of Maine in Orono. He is the author of “Health, Illness, and Society: An Introduction to Medical Sociology.” He is a member of the Maine chapter of the national Scholars Strategy Network, which brings together scholars across the country to address public challenges and their policy implications. Members’ columns appear in the BDN every other week.